High integration of semiconductor memory devices has been ongoing. However, a method for increasing a degree of integration according to improvement of a lithography technique is getting closer to the limit. Therefore, there has been proposed a stacked type memory device in which electrode films and insulating films are alternately stacked to form a stacked body, through-holes are collectively formed in the stacked body, a memory film is formed on the inner surfaces of the through-holes, and thereafter silicon pillars are formed on the insides of the through-holes. In the stacked type memory device, memory cells including the memory film as a charge storage member are formed in crossing portions of the silicon pillars and the electrode films. Therefore, the memory cells are three-dimensionally arrayed.
As a first example of the stacked type memory device, there has been proposed a memory device of an I-shaped pillar type in which source lines are provided under a stacked body, bit lines are provided on the stacked body, the lower ends of silicon pillars are connected to the source lines, and the upper ends of the silicon pillars are connected to the bit lines. However, when the memory device of the I-shaped pillar type is manufactured, in order to connect the silicon pillars to the source lines after forming a memory film on the inner surfaces of through-holes, the memory film from the bottoms of the through-holes needs to be removed by etching or the like. When the memory film is removed, the memory film formed on the side surfaces of the through-holes, that is, the memory film forming memory cells is damaged.
As a second example of the stacked type memory device, there has been proposed a memory device of a U-shaped pillar type in which source lines and bit lines are provided on a stacked body, upper end portions of two silicon pillars are respectively connected to the source lines and the bit lines, and the lower end portions of the two silicon pillars are connected via a connecting member. When the memory device of the U-shaped pillar type is manufactured, by causing two through-holes to communicate with a space in which the connecting member is planned to be formed, it is possible to form a memory film on the inner surfaces of the through-holes and a hollow and thereafter integrally form the silicon pillars and the connecting member. Therefore, it is unnecessary to remove the memory film on the bottoms of the through-holes. However, in the memory device of the U-shaped pillar type, the number of memory cells connected in series between the source lines and the bit lines increases. Therefore, a control circuit is large. Further, since a current path between the source lines and the bit lines is long, ON resistance is high.